DESCRIPTION Continued support of six predoctoral and four postdoctoral trainees in the studies of mutagens and carcinogens is requested for the next five years. Professor Stuart M. Linn will continue to serve as the training program director along with the previous training faculty members: Drs. B. Ames, M. Botchan, N. Cozzarelli, and J. Rine. Three new members with expertise in Nutritional Sciences (L. Bjeldanes) and Public Health/Epidemiology (A. Smith and M. Smith) have been recruited to replace Drs. J. Hearst, I. Tinoco (retired), and H. Echols (deceased). Predoctoral trainees are to be recruited from the graduate students of the Molecular and Cellular Biology (MCB), Nutritional Sciences (NS), Environmental Health Sciences (EHS), and to a lesser degree, the Chemistry program. Graduate students are selected by the Graduate Admissions Committees of the individual departments based on research experience, letters of recommendation, GPA (after adjustment for degrees of difficulty), and GRE scores (both the general and achievement tests). The admission rates vary from 40-50% in EHS to 10-25% in MCB and NS. Postdoctoral trainees apply directly to a particular laboratory and are selected on the basis of research interests, previous experience and performance, and whenever possible, personal interviews and presentations. The emphasis of predoctoral training is on teaching students "to think imaginatively and critically about scientific issues, to select important fundamental problems, to choose the most feasible and incisive approaches to address the problem chosen, to design and implement the actual experiments undertaken, to analyze the data exhaustively, and to have the insight to pursue the questions that arise in the most fruitful directions". It takes, on average, over five years to complete the doctoral program. Students in their first year are committed to course work, laboratory rotations, and selection of a thesis advisor. The second year training includes continued course work, training in teaching, thesis research, and completion of qualifying examination. Thesis research for each trainee will be continued in year 3 and beyond until the doctoral dissertation is completed. Research progress of each trainee is monitored through regularly scheduled meetings with the research advisor or a departmental graduate advisor, and the entire Thesis Committee (appointed by the graduate division) once the student has passed the qualifying examination. Research advisor also meets each trainee in group meetings, affinity groups, and weekly journal clubs. In addition, the rich variety of course offerings and the wide range of seminar series and special lectureships provide both breadth and depth to the training program. Postdoctoral trainees may elect to attend individual lectures or entire courses; they also direct undergraduate research and occasionally lead undergraduate seminars. They become independent investigators capable of teaching, research, and training students at the end of their training programs.